Corrosion Inhibition

ABSTRACT

The present invention provides a lubricating composition containing (a) an oil of lubricating viscosity; (b) a corrosion inhibitor; and (c) an antiwear agent comprising at least one of (i) polyhydric alcohol with oxyalkylene groups, (ii) a fatty amine, or (iii) mixtures thereof, wherein the lubricating composition has a total sulphated ash content of less than 0.8 wt %. The invention further provides for the use of the lubricating composition in an internal combustion engine.

FIELD OF INVENTION

The present invention relates to corrosion inhibition in a lubricating composition with a low total sulphated ash content. The invention further relates to the use of the lubricating composition in a internal combustion engine.

BACKGROUND OF THE INVENTION

Corrosion inhibitors are known and have been utilised in a variety of lubricant formulations. However, corrosion inhibitors are rarely used in a lubricant, e.g., an engine lubricant, because of their known adverse effect on the performance of antiwear chemistry, particularly zinc dialkyl dithiophosphate (ZDDP). Consequently the absence of corrosion inhibitors results in an increase in corrosion. Conversely the presence of corrosion inhibitors reduces antiwear performance resulting in increased wear.

Therefore it would be advantageous to have a lubricating composition with acceptable corrosion inhibition and antiwear performance. The present invention provides a lubricating composition with acceptable corrosion inhibition and antiwear performance.

SUMMARY OF THE INVENTION

The invention provides a lubricating composition comprising:

-   -   (a) an oil of lubricating viscosity;     -   (b) a corrosion inhibitor; and     -   (c) an antiwear agent comprising at least one of (i) polyhydric         alcohol with oxyalkylene groups, (ii) a fatty amine, or (iii)         mixtures thereof,         wherein the lubricating composition has a sulphated ash content         of less than 0.8 wt %.

DETAILED DESCRIPTION OF THE INVENTION

The invention provides a lubricating composition as defined above.

In one embodiment the lubricating composition has a total sulphated ash content of 0.75 wt % or less, 0.7 wt % or less, 0.65 wt % or less, 0.6 wt % or less, or 0.5 wt % or less. Examples of suitable ranges for the total sulphated ash content include 0.01 wt % to 0.68 wt %, or 0.1 wt % to 0.63 wt %, or 0.2 wt % to 0.55 wt %.

In one embodiment the lubricating composition has a phosphorus content of 900 ppm or less, 800 ppm or less or 750 ppm or less. Examples of suitable ranges include 50 ppm to 850 ppm of phosphorus, 100 ppm to 700 ppm of phosphorus or 150 ppm to 500 ppm.

In one embodiment the lubricating composition has a sulphur content of less than 3000 ppm, 2000 ppm or less, 1500 ppm or less or 1000 ppm or less. Examples of suitable ranges include 50 ppm to 1750 ppm, or 50 ppm to 2000 ppm of sulphur, 200 ppm to 1250 ppm of sulphur or 300 ppm to 900 ppm of sulphur.

Oil of Lubricating Viscosity

The lubricating oil composition includes natural or synthetic oils of lubricating viscosity, oil derived from hydrocracking, hydrogenation, hydrofinishing, and unrefined, refined and re-refined oils and mixtures thereof.

Natural oils include animal oils, vegetable oils, mineral oils and mixtures thereof. Synthetic oils include hydrocarbon oils, silicon-based oils, and liquid esters of phosphorus-containing acids. Synthetic oils may be produced by Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils. In one embodiment the polymer composition of the present invention is useful when employed in a gas-to-liquid oil. Often Fischer-Tropsch hydrocarbons or waxes may be hydroisomerised.

Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. In one embodiment the oil of lubricating viscosity comprises an API Group I, II, III, IV, V, VI or mixtures thereof, and in another embodiment API Group I, II, III or mixtures thereof. If the oil of lubricating viscosity is an API Group II, III, IV, V or VI oil there may be up to 40 wt % and in another embodiment up to a maximum of 5 wt % of the lubricating oil an API Group I oil present.

The oil of lubricating viscosity in one embodiment is present from 15 wt % to 99.9 wt % of the composition, in another embodiment from 30 wt % to 98.9 wt % of the composition, in another embodiment from 40 wt % to 97.9 wt % of the composition, in another embodiment and in another embodiment from 50 wt % to 94.5 wt % of the composition.

Corrosion Inhibitors

The lubricating composition contains a corrosion inhibitor.

In one embodiment the corrosion inhibitor is a polyhydric alcohol. In one embodiment the corrosion inhibitor comprises a polyhydric alcohol with oxyalkylene groups. In one embodiment the corrosion inhibitor comprises a polyhydric alcohol comprising monomeric units of oxyalkylene groups. The polyhydric alcohol is often aliphatic, cycloaliphatic, aromatic, or heterocyclic. The polyhydric alcohol may be selected from the group consisting of aliphatic-substituted cycloaliphatic alcohols, aliphatic-substituted aromatic alcohols, aliphatic-substituted heterocyclic alcohols, cycloaliphatic-substituted aliphatic alcohols, cycloaliphatic-substituted aromatic alcohols, cycloaliphatic-substituted heterocyclic alcohols, heterocyclic-substituted aliphatic alcohols, heterocyclic-substituted cycloaliphatic alcohols, heterocyclic-substituted aromatic alcohols or mixtures thereof.

The polyhydric alcohol typically contains 2 to 10, 2 to 6 or 2 to 4 hydroxy groups. The polyhydric alcohol may be derived from a polyglycol contain up to 150, up to 100, up to 75 or up to 50 oxyalkylene groups. The oxyalkylene group may be present in repeat units present from 2 to 150 repeat units, or 2 to 125 repeat units, 4 to 90 repeat units, or 6 to 45 repeat units. Each oxyalkylene group may independently contain a number of carbon atoms present from 2 to 8, 2 to 5 or 3 to 4. In one embodiment the oxyalkylene group contains 3 or 4 carbon atoms.

Other examples of polyhydric alcohols include glycols such as ethylene glycol, propylene glycol, butylene glycol, pentaerthyritol, mannitol, sorbitol, glycerol, di-glycerol, tri-glycerol, tetra-glycerol, erythritol, 2-hydroxymethyl-2-methyl-1,3-propanediol (trimethylolethane), 2-ethyl-2-(hydroxymethyl)-1,3-propanediol (trimethylolpropane), 1,2,4-hexanetriol and mixtures thereof.

Examples of a suitable polyhydric alcohol corrosion inhibitor include a polyalkylene glycol called Pluriol® commercially available from BASF, or Synalox® 100-20B, Synalox® 100-30B, Synalox® 100-50B, Synalox® 100-85B, Synalox® 100-120B or Synalox® 100-150B (all commercially available from Dow). The Synalox® corrosion inhibitors are polyhydric alcohol with oxyalkylene groups that is, poly or oligo-oxyalkylene groups, with very low pour points and high viscosity indices. Typically the Synalox® corrosion inhibitor comprises a homopolymer or copolymer of propylene oxide. The Synalox® corrosion inhibitor is described in more detail in a product brochure with Form No. 118-01453-0702 AMS, published by The Dow Chemical Company. The product brochure is entitled “SYNALOX Lubricants, High-Performance Polyglycols for Demanding Applications.”

When the corrosion inhibitor comprises the polyhydric alcohol with poly- or oligo-oxyalkylene groups, typically, the monomeric oxyalkylene groups contain at least 50 wt % or at least 65 wt % or at least 80 wt % or at least 95 wt %, groups of 3 to 8 carbon atoms. In some instances, a number of oxyalkylene groups may be ethylene oxide, provided the corrosion inhibitor is oil soluble.

In one embodiment the corrosion inhibitor comprises a fatty amine or amide, such as an oil soluble saturated or unsaturated alkylated amine or derivatives thereof. In one embodiment the amine is a monoamine and in another embodiment the amine is a polyamine. In one embodiment the fatty amine has a terminal —NH₂ group.

Examples of a suitable fatty amine include oleyl amine, octylamine octanoate or the reaction product of a fatty acid such as oleic acid with a polyamine or mixtures thereof.

In another embodiment the corrosion inhibitor includes condensation products of dodecenyl succinic acid or anhydride.

In one embodiment the corrosion inhibitor may be a the same as a metal deactivator, i.e., derivatives of benzotriazoles, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles or 2-alkyldithiobenzothiazoles. The benzotriazole compounds may be substituted at one of the following ring positions 1- or 2- or 4- or 5- or 6- or 7-benzotriazoles. The hydrocarbyl groups contain 1 to 30, 1 to 15 or 1 to 7 carbon atoms. Examples of a benzotriazole include tolylbenzotriazole.

Often the corrosion inhibitor is present from 0.01 to 10, in one embodiment 0.01 to 5, in another embodiment 0.02 to 2 and in yet another embodiment 0.05 to 1 weight percent of the lubricating composition. The corrosion inhibitor agent may be used alone or in combination.

Antiwear Agent

The lubricating composition contains an antiwear agent. In one embodiment the antiwear agent is a metal hydrocarbyl dithiophosphate. The hydrocarbyl group in one embodiment in an alkyl or cycloalkyl group with 1 to 30, in another embodiment 3 to 10 and in yet another embodiment 3 to 8 carbon atoms.

The metal includes mono- or di- or tri-valent metal, in one embodiment divalent and in another embodiment a divalent transition metal. In one embodiment the metal is zinc, in another embodiment calcium or barium.

Examples of a metal hydrocarbyl dithiophosphate include zinc dihydrocarbyl dithiophosphates (often referred to as ZDDP, ZDP or ZDTP). Examples of suitable zinc hydrocarbyl dithiophosphates compounds may include the reaction product(s) of heptylated or octylated or nonylated dithiophosphoric acids with ethylene diamine, morpholine or mixtures thereof.

In an alternative embodiment the antiwear agent is ashless i.e. the antiwear agent is metal-free (prior to mixture with other components). Often the metal-free antiwear agent is an amine salt. The ashless antiwear agent often contains an atom including sulphur, phosphorus, boron or mixtures thereof.

The amine is often a primary amine, a secondary amine a tertiary amine or mixtures thereof. Often a primary amine and/or a secondary amine will contain at least one hydrocarbyl group with the number of carbon atoms present from 2 to 30, in one embodiment 8 to in one embodiment 26, in another embodiment 10 to 20, and in yet another embodiment 11 to 18.

Examples of primary amines useful in the present invention include ethylamine, propylamine, butylamine, 2-ethylhexylamine, octylamine and dodecylamine. Also suitable primary fatty amines which include n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine and oleyamine. Other useful fatty amines include commercially available fatty amines such as “Armeen®” amines (products available from Akzo Chemicals, Chicago, Ill.), such as Armeen C, Armeen O, Armeen OL, Armeen T, Armeen HT, Armeen S and Armeen SD, wherein the letter designation relates to the fatty group, such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine and ethylamylamine. The secondary amines may be cyclic amines such as piperidine, piperazine and morpholine.

The amine may also be a tertiary-aliphatic primary amine. Often the aliphatic group is an alkyl group containing a number of carbon atoms from 2 to 30, in one embodiment 6 to 26 and in another embodiment 8 to 24. Often the tertiary alkyl primary amines are monoamines such as tert-butylamine, terthexylamine, 1-methyl-1-amino-cyclohexane, tert-octylamine, tert-decylamine, tertdodecylamine, tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine, terttetracosanylamine, and tert-octacosanylamine.

Mixtures of amines may also be used in the invention. Especially useful mixtures of amines are “Primene 81R” and “Primene JMT.” Primene 81R and Primene JMT (both produced and sold by Rohm & Haas) are mixtures of C₁₁ to C₁₄ tertiary alkyl primary amines and C₁₈ to C₂₂ tertiary alkyl primary amines respectively.

The ashless antiwear agent may also include phosphoric acid esters or salt thereof; dialkyldithiophosphoric acid esters or salt thereof; phosphites; and phosphorus-containing carboxylic esters, ethers, and amides or mixtures thereof.

Other ashless antiwear agent compounds include sulphur-containing ashless anti-wear additives are thiocarbamate-containing compounds, such as thiocarbamate esters, thiocarbamate amides, thiocarbamic ethers, alkylene-coupled thiocarbamates, and bis(S-alkyldithiocarbamyl) disulfides.

The dithiocarbamate-containing compounds may be prepared by reacting a dithiocarbamate acid or salt with an unsaturated compound. The dithiocarbamate containing compounds may also be prepared by simultaneously reacting an amine, carbon disulfide and an unsaturated compound. Generally, the reaction occurs at a temperature from 25° C. to 125° C. U.S. Pat. Nos. 4,758,362 and 4,997,969 describe dithiocarbamate compounds and methods of making them.

Useful fatty amines include commercially available fatty amines such as “Armeen”® amines (products available from Akzo Chemicals, Chicago, Ill.), such as Akzo's, Armeen C, Armeen O, Armeen OL, Armeen T, Armeen HT, Armeen S and Armeen SD, wherein the letter designation relates to the fatty group, such as coco, oleyl, tallow, or stearyl groups.

In an alternative embodiment of the invention, the ashless antiwear agent may be a monoester of a polyol and an aliphatic carboxylic acid, often an acid containing 12 to 24 carbon atoms. Often the monoester of a polyol and an aliphatic carboxylic acid is in the form of a mixture with a sunflower oil or the like, which may be present in the friction modifier mixture from 5 to 95, in one embodiment 10 to 90, in another embodiment 20 to 85 and in yet another embodiment 20 to 80 weight percent of said mixture. The aliphatic carboxylic acids (especially a monocarboxylic acid) which form the esters are those acids containing 12 to 24 carbon atoms and in one embodiment 14 to 20 carbon atoms. Examples of carboxylic acids include dodecanoic acid, stearic acid, lauric acid, behenic acid, and oleic acid.

Polyols include diols, triols, and alcohols with higher numbers of alcoholic OH groups. Polyhydric alcohols include ethylene glycols, including di-, tri- and tetraethylene glycols; propylene glycols, including di-, tri- and tetrapropylene glycols; glycerol; butane diol; hexane diol; sorbitol; arabitol; mannitol; sucrose; fructose; glucose; cyclohexane diol; erythritol; and pentaerythritols, including di- and tripentaerythritol. Often the polyol is diethylene glycol, triethylene glycol, glycerol, sorbitol, pentaerythritol or dipentaerythritol.

The commercially available monoester known as “glycerol monooleate” is believed to include 60±5 percent by weight of the chemical species glycerol monooleate, along with 35×5 percent glycerol dioleate, and less than 5 percent trioleate and oleic acid. The amounts of the monoesters, described above, are calculated based on the actual, corrected, amount of polyol monoester present in any such mixture.

In one embodiment of the invention the antiwear agent is a borated ester. The borated ester may be prepared by the reaction of a boron compound and at least one compound selected from epoxy compounds, halohydrin compounds, epihalohydrin compounds, alcohols and mixtures thereof. Typically the alcohols include monohydric alcohols, dihydric alcohols, trihydric alcohols or higher alcohols.

Boron compounds suitable for preparing the borate ester include a boric acid (including metaboric acid, HBO₂, orthoboric acid, H₃BO₃, and a tetraboric acid, H₂B₄O₇), a boric oxide, a boron trioxide and an alkyl borate. The borate ester may also be prepared from boron halides. The borated ester further contains at least one hydrocarbyl group often containing about 8 to about 30 carbon atoms.

Often the antiwear agent is present from 0.01 to 20, in one embodiment 0.01 to 10, in one embodiment 0.01 to 5, in another embodiment 0.02 to 4 and in yet another embodiment 0.05 to 2.5 weight percent of the lubricating composition. The antiwear agent may be used alone or in combination.

Other Performance Additives

The composition of the invention optionally further includes at least one other performance additive. The other performance additives include metal deactivators, detergents, dispersants, viscosity modifiers, friction modifiers, dispersant viscosity modifiers, extreme pressure agents, antioxidant, foam inhibitors, demulsifiers, pour point depressants, seal swelling agents and mixtures thereof.

The total combined amount of the other performance additives present ranges from 0 wt % to 25 wt %, in one embodiment 0.01 wt % to 20 wt %, in another embodiment 0.1 wt % to 15 wt % and in yet another embodiment 0.5 wt % to 10 wt % of the lubricating composition. Although one or more of the other performance additives may be present, it is common for the other performance additives to be present in different amounts relative to each other.

If the present invention is in the form of a concentrate (which may be combined with additional oil to form, in whole or in part, a finished lubricant), the amount of each of the above-mentioned additives, as well as the other performance additives, will be present in a concentration which is approximately 5 or 10-fold greater than the values given. The amount of oil will be correspondingly reduced.

Viscosity Modifier

In one embodiment the lubricating composition further comprises a viscosity modifier. Viscosity modifiers include styrene-butadiene rubbers, ethylene-propylene copolymers, hydrogenated styrene-isoprene polymers, hydrogenated isoprene polymers, polyalkyl styrenes, polyolefins, polyalkylmethacrylates and esters of maleic anhydride-styrene copolymers, or mixtures thereof. In one embodiment the polymeric thickener is poly(meth)acrylate.

The polymeric thickener has a weight average molecular weight (Mw) of at least 10,000, in another embodiment at least 15,000, in another embodiment at least 25,000 and in another embodiment at least 35,000. The polymeric thickener generally has no upper limit on Mw, however in one embodiment the Mw is less than 2,000,000 in another embodiment less than 500,000 and in another embodiment less than 150,000. Examples of suitable ranges of Mw include in one embodiment 12,000 to 1,000,000, in another embodiment 20,000 to 300,000 and in another embodiment 30,000 to 75,000.

Antioxidants include a molybdenum dithiocarbamate, a sulphurised olefin, a hindered phenol, a diphenylamine; detergents include neutral or overbased, Newtonian or non-Newtonian, basic salts of alkali, alkaline earth and transition metals with one or more substrates. Typically the substrates include a substituted phenol (forms a phenate), a sulphur bridging substituted phenol (forms a sulphurised phenate), a sulphonic acid (forms a sulphonate (often a calcium sulphonate detergent with a TBN ranging from 300 to 500, or 330 to 450), a carboxylic acid (forms a carboxylate), a phosphorus acid (forms a phosphonate), a mono- and/or a di-thiophosphoric acid (forms a thiophosphonate), a saligenin, an alkyl salicyclic acid (forms alkylsalicylates), a salixarate; dispersants include N-substituted long chain alkenyl succinimides as well as posted treated versions thereof; post-treated dispersants include those by reaction with urea, thiourea, dimercaptothiadiazoles, carbon disulphide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, nitriles, epoxides, boron compounds, and phosphorus compounds; and metal deactivators including derivatives of benzotriazoles, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles or 2-alkyldithiobenzothiazoles may also be used.

Antiscuffing agents including organic sulphides and polysulphides, such as benzyldisulphide, bis-(chlorobenzyl) disulphide, dibutyl tetrasulphide, di-tertiary butyl polysulphide, di-tert-butylsulphide, sulphurised Diels-Alder adducts or alkyl sulphenyl N′N-dialkyl dithiocarbamates; extreme pressure (EP) agents including chlorinated wax, organic sulphides and polysulphides, such as benzyldisulphide, bis-(chlorobenzyl) disulphide, dibutyl tetrasulphide, sulphurised methyl ester of oleic acid, sulphurised alkylphenol, sulphurised dipentene, sulphurised terpene, and sulphurised Diels-Alder adducts. Phosphosulphurised hydrocarbons, metal thiocarbamates, such as zinc dioctyldithiocarbamate and barium heptylphenol diacid; friction modifiers including fatty amines, esters such as borated glycerol esters, fatty phosphites, fatty acid amides, fatty epoxides, borated fatty epoxides, alkoxylated fatty amines, borated alkoxylated fatty amines, metal salts of fatty acids, fatty imidazolines, condensation products of carboxylic acids and polyalkylene-polyamines, amine salts of alkylphosphoric acids; and dispersant viscosity modifiers (often referred to as DVM) include functionalised polyolefins, for example, ethylene-propylene copolymers that have been functionalized with the reaction product of maleic anhydride and an amine, a polymethacrylate functionalised with an amine, or esterified styrene-maleic anhydride copolymers reacted with an amine.

Other performance additives such as foam inhibitors including copolymers of ethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate; demulsifiers including trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene, polymethacrylates, polyacrylates or polyacrylamides; and seal swell agents including Exxon Necton-37™ (FN 1380) and Exxon Mineral Seal Oil (FN 3200) may also be used in the composition of the invention.

Process

The lubricating composition of the invention may be prepared by a process comprising blending:

-   -   (a) an oil of lubricating viscosity;     -   (b) a corrosion inhibitor; and     -   (c) an antiwear agent,         wherein the lubricating composition has a total sulphated ash         content of less than 0.8 wt %.

In one embodiment the blending conditions are typically 15° C. to 130° C., in one embodiment 20° C. to 120° C. and in another embodiment 25° C. to 110° C.; and for a period of time in the range 30 seconds to 48 hours, in one embodiment 2 minutes to 24 hours, and in another embodiment 5 minutes to 16 hours; and at pressures in the range 86.4 kPa to 266 kPa (650 mm Hg to 2000 mm Hg), in one embodiment 91.8 kPa to 200 kPa (690 mm Hg to 1500 mm Hg), and in another embodiment 95.1 kPa to 133 kPa (715 mm Hg to 1000 mm Hg).

The process optionally includes mixing other performance additives as described above. The optional performance additives may be added sequentially, separately or as a concentrate.

Industrial Application

The lubricating composition of the present invention is useful for an internal combustion engine, for example a diesel fuelled engine, a gasoline fuelled engine, a natural gas fuelled engine or a mixed gasoline/alcohol fuelled engine. In one embodiment the internal combustion engine is a diesel fuelled engine and in another embodiment a gasoline fuelled engine.

In one embodiment the invention provides a method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the composition as described herein. The use of the composition may impart one or more of corrosion inhibition and antiwear performance.

In one embodiment the invention provides the use of a polyhydric alcohol comprising monomeric units of oxyalkylene groups with 2 to 8 carbon atoms as a corrosion inhibitor in a lubricating composition.

The following examples provide an illustration of the invention. These examples are non exhaustive and are not intended to limit the scope of the invention.

EXAMPLES Reference Example 1 Oleyl Amine Corrosion Inhibitor In API Group III Oil

Reference Example 1 is prepared by blending into an oil of lubricating viscosity comprising a Nexbase™ oil with a viscosity of 4.3 mm² s⁻¹, 12.1 wt % of a viscosity modifier, 11.4 wt % of other additives including an effective amount of an antiwear agent. The composition has a total sulphated ash content of greater than 1 wt %, a phosphorus content of greater than 960 ppm and a sulphur content of greater than 3000 ppm.

Reference Example 2 Oleyl Amine Corrosion Inhibitor In API Group III Oil

Reference Example 2 is the same as Reference Example 1, except 0.5 wt % of oleyl amine is additionally blended

Reference Example 3 Oleyl Amine Corrosion Inhibitor In API Group IV Oil

Reference Example 3 is prepared by blending 0.5 wt % of oleyl amine into an oil of lubricating viscosity comprising 49.9 wt % of a PAO-6 with 9 wt % of a viscosity modifier, 14.2 wt % of other additives including an effective amount of an antiwear agent. The composition has a total sulphated ash content of greater than 1 wt %, a phosphorus content of greater than 960 ppm and a sulphur content of greater than 3000 ppm.

Example 1

Example 1 is prepared by blending 0.1 wt % of Pluriol® corrosion inhibitor into a lubricating composition comprising a Nexbase™ oil with a viscosity of 4.3 mm² s⁻¹, 12.1 wt % of a viscosity modifier, 11.4 wt % of other additives including an effective amount of an antiwear agent. The composition has a total sulphated ash content of less than 0.08 wt %, a phosphorus content of less than 960 ppm and a sulphur content of less than 3000 ppm.

Example 2

Example 2 is the same as Example 1, except the amount of Pluriol® corrosion inhibitor present is 0.2 wt %.

Example 3

Example 3 is the same as Example 1, except the corrosion inhibitor is oleyl amine present at 0.1 wt %.

Example 4

Example 4 is the same as Example 3, except the oleyl amine is present at 0.2 wt %.

Example 5

Example 5 is the same as Example 1, except the corrosion inhibitor is Synalox® 100-120B present at 0.1 wt %.

Example 6

Example 6 is the same as Example 5, except the corrosion inhibitor is Synalox® 100-120B present at 0.2 wt %.

Test 1: PV1401 Corrosion Test

The PV1401 is a Volkswagen corrosion prevention test. The test requires submersing steel plates in an oil of lubricating viscosity followed by draining the oil off the plate and then suspending the plate in a sealed moist chamber at 50° C. and 100 % humidity. The plates are then analysed to determine the amount of corrosion by classifying the degree of corrosion on a scale of 1 to 5 summarised in Table 1:

TABLE 1 Degree of corrosion Significance Description 1 No corrosion Complete surface unchanged 2 Traces of corrosion 5 rust points/surface max. 3 Slight corrosion Up to 5% surface corrosion 4 Moderate corrosion Over 5 to 20% surface corrosion 5 Strong corrosion Over 20% surface corrosion

Overall the data indicates that the lubricating composition of the invention with a sulphated ash content of 0.8 wt % or less has improved corrosion inhibition without adversely affecting antiwear performance over a similar composition containing a sulphated ash content of above 1 wt %.

In summary the invention provides a lubricating composition with corrosion inhibition and antiwear performance in a low sulphated ash engine lubricant.

Each of the documents referred to above is incorporated herein by reference. Except in the Examples, or where otherwise explicitly indicated, all numerical quantities in this description specifying amounts of materials, reaction conditions, molecular weights, number of carbon atoms, and the like, are to be understood as modified by the word “about.” Unless otherwise indicated, each chemical or composition referred to herein should be interpreted as being a commercial grade material which may contain the isomers, by-products, derivatives, and other such materials which are normally understood to be present in the commercial grade. However, the amount of each chemical component is presented exclusive of any solvent or diluent oil, which may be customarily present in the commercial material, unless otherwise indicated. It is to be understood that the upper and lower amount, range, and ratio limits set forth herein may be independently combined. Similarly, the ranges and amounts for each element of the invention may be used together with ranges or amounts for any of the other elements. As used herein all of the ranges allow for the components to contain normal commercially known amounts of diluent oil often used as a carrier fluid. Consequently the ranges given above for the additives may contain a portion of diluent oil.

As used herein, the expression “consisting essentially of” permits the inclusion of substances that do not materially affect the basic and novel characteristics of the composition under consideration. As used herein any member of a genus (or list) may be excluded from the claims.

As used herein, the term “hydrocarbyl substituent” or “hydrocarbyl group” is used in its ordinary sense, which is well-known to those skilled in the art. Specifically, it refers to a group having a carbon atom directly attached to the remainder of the molecule and having predominantly hydrocarbon character. Examples of hydrocarbyl groups include:

-   -   hydrocarbon substituents, that is, aliphatic (e.g., alkyl or         alkenyl), alicyclic (e.g., cycloalkyl, cycloalkenyl)         substituents, and aromatic-, aliphatic-, and         alicyclic-substituted aromatic substituents, as well as cyclic         substituents wherein the ring is completed through another         portion of the molecule (e.g., two substituents together form a         ring);     -   substituted hydrocarbon substituents, that is, substituents         containing non-hydrocarbon groups which, in the context of this         invention, do not alter the ,predominantly hydrocarbon nature of         the substituent (e.g., halo (especially chloro and fluoro),         hydroxy, alkoxy, mercapto, alkylmercapto, nitro, nitroso, and         sulfoxy);     -   hetero substituents, that is, substituents which, while having a         predominantly hydrocarbon character, in the context of this         invention, contain other than carbon in a ring or chain         otherwise composed of carbon atoms. Heteroatoms include sulphur,         oxygen, nitrogen, and encompass substituents as pyridyl, furyl,         thienyl and imidazolyl. In general, no more than two, in one         embodiment no more than one, non-hydrocarbon substituent will be         present for every ten carbon atoms in the hydrocarbyl group;         typically, there will be no non-hydrocarbon substituents in the         hydrocarbyl group. 

1. A lubricating composition comprising: (a) an oil of lubricating viscosity; (b) an antiwear agent; and (c) a polyhydric alcohol corrosion inhibitor comprising monomeric units of oxyalkylene groups, wherein the lubricating composition has a total sulphated ash content of less than 0.8 wt %.
 2. The lubricating composition of claim 1, wherein the polyhydric alcohol contains 2 to 150 oxyalkylene groups.
 3. The lubricating composition of claim 1, wherein the oxyalkylene groups contain 3 or 4 carbon atoms.
 4. The lubricating composition of claim 1, wherein the corrosion inhibitor contains oxyalkylene groups with of 3 to 8 carbon atoms on at least 65 wt % of the oxyalkylene groups.
 5. The lubricating composition of claim 1, wherein the total sulphated ash content is 0.7 wt % or less.
 6. The lubricating composition of claim 1, wherein the composition has a phosphorus content of 900 ppm or less.
 7. The lubricating composition of claim 1, wherein the composition has a sulphur content of 50 ppm to 2000 ppm.
 8. The lubricating composition of claim 1, wherein the lubricating composition has a phosphorus content of 100 ppm to 700 ppm; and the lubricating composition has a sulphur content of less than 3000 ppm.
 9. The lubricating composition of claim 1, wherein the antiwear agent comprises a metal hydrocarbyl dithiophosphate.
 10. The lubricating composition of claim 1 further comprising a viscosity modifier.
 11. The lubricating composition of claim 10, wherein the viscosity modifier includes at least one of styrene-butadiene rubbers, ethylene-propylene copolymers, hydrogenated styrene-isoprene polymers, hydrogenated isoprene polymers, polyalkyl styrenes, polyolefins, polyalkylmethacrylates and esters of maleic anhydride-styrene copolymers, or mixtures thereof.
 12. The lubricating composition of claim 10, wherein the viscosity modifier has a Mw of 20,000 to 300,000.
 13. The lubricating composition of claim 1, wherein the corrosion inhibitor is present from 0.01 to 10 weight percent of the lubricating composition.
 14. A method for lubricating an internal combustion engine, comprising supplying thereto a lubricant comprising the composition
 1. 15. (canceled) 